The two-decade-old talks have not fulfilled their main purpose: reducing the greenhouse gas emissions that scientists say are warming the planet.

Attempts to create a new climate treaty failed in Copenhagen three years ago but countries agreed last year to try again, giving themselves a deadline of 2015 to adopt a new treaty.

Several issues need to be resolved by then, including how to spread the burden of emissions cuts between rich and poor countries. That's unlikely to be decided in the Qatari capital of Doha, where negotiators will focus on extending the Kyoto Protocol, an emissions deal for industrialized countries, and trying to raise billions of dollars to help developing countries adapt to a shifting climate.

"We owe it to our people, the global citizenry. We owe it to our children to give them a safer future than what they are currently facing," said South African Foreign Minister Maite Nkoana-Mashabane, who led last year's talks in Durban, South Africa.

The U.N. process is often criticized, even ridiculed, both by climate activists who say the talks are too slow, and by those who challenge the scientific near-consensus that the global temperature rise is at least partly caused by human activity, primarily the burning of fossil fuels like coal and oil.

Environmentalists found the choice of Qatar as host of the two-week conference ironic. The tiny Persian Gulf emirate owes its wealth to large resources of gas and oil and emits more greenhouse gases per capita than any other nation.

Yet it hasn't announced any climate action in the U.N. process, and former Qatari oil minister Abdullah Bin Hamad Al-Attiyah didn't do so when he opened the conference Monday.

"We should not concentrate on the per capita (emissions), we should concentrate on the amount from each country," Al-Attiyah told reporters. "I think Qatar is the right place to host" the conference, he added.

The concentration of greenhouse gases such as carbon dioxide has jumped 20 percent since 2000, according to a U.N. report released last week. The report also showed that there is a growing gap between what governments are doing to curb emissions and what needs to be done to protect the world from potentially dangerous levels of warming.

The goal of the U.N. talks is to keep the global temperature rise under 2 degrees C (3.6 F), compared to pre-industrial times.

But efforts taken so far to rein in emissions, reduce deforestation and promote clean technology are not getting the job done. A recent projection by the World Bank showed temperatures are expected to increase by up to 4 degrees C (7.2 F) by 2100.

"Climate change is no longer some distant threat for the future, but is with us today," said Greenpeace climate campaigner Martin Kaiser, who was also at the Doha talks. "At the end of a year that has seen the impacts of climate change devastate homes and families around the world, the need for action is obvious and urgent."

Dangerous warming effects could include flooding of coastal cities and island nations, disruptions to agriculture and drinking water, the spread of diseases and the extinction of species.

Many scientists also say that extreme weather events, such as Hurricane Sandy's onslaught on the U.S. East Coast, will become more frequent as the Earth warms, although it is impossible to attribute any individual event to climate change.

The Kyoto Protocol, adopted in 1997, is the most important climate agreement reached in the U.N. process so far. It expires this year, so negotiators in Doha will try to extend it as a stopgap measure until a wider deal can be reached. […]